Low power and Lossy Networks (LLNs), e.g., sensor networks, have a myriad of applications, such as Smart Grid (smart metering), home and building automation, smart cities, etc. Various challenges are presented with LLNs, such as lossy links, low bandwidth, battery operation, low memory and/or processing capability, etc. Routing in LLNs is undoubtedly one of the most critical challenges and a core component of the overall networking solution. Two fundamentally and radically different approaches, each with certain advantages and drawbacks, have been envisioned for routing in LLN/ad-hoc networks known as:
1) Proactive routing: routing topologies are pre-computed by the control plane (e.g., IS-IS, OSPF, RIP, and RPL are proactive routing protocols); and
2) Reactive routing: routes are computed on-the-fly and on-demand by a node that sends discovery probes throughout the network (e.g., AODV, DYMO, and LOAD are reactive routing protocols), usually driven by user packets to be sent over the network.